From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f70.google.com (mail-pa0-f70.google.com [209.85.220.70]) by kanga.kvack.org (Postfix) with ESMTP id D89C06B025E for ; Thu, 29 Sep 2016 09:15:10 -0400 (EDT) Received: by mail-pa0-f70.google.com with SMTP id cg13so140417962pac.1 for ; Thu, 29 Sep 2016 06:15:10 -0700 (PDT) Received: from mga03.intel.com (mga03.intel.com. [134.134.136.65]) by mx.google.com with ESMTPS id tj3si14348525pab.171.2016.09.29.06.15.09 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 29 Sep 2016 06:15:09 -0700 (PDT) Message-ID: <1475154880.16655.9.camel@vmm.sh.intel.com> Subject: Re: [PATCH v3 1/2] mm, proc: Fix region lost in /proc/self/smaps From: Robert Hu Reply-To: robert.hu@intel.com Date: Thu, 29 Sep 2016 21:14:40 +0800 In-Reply-To: <20160926084616.GA28550@dhcp22.suse.cz> References: <1474636354-25573-1-git-send-email-robert.hu@intel.com> <20160923135635.GB28734@redhat.com> <20160923145301.GU4478@dhcp22.suse.cz> <20160923155351.GA1584@redhat.com> <20160926084616.GA28550@dhcp22.suse.cz> Content-Type: text/plain; charset="ISO-8859-15" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Oleg Nesterov , Robert Ho , pbonzini@redhat.com, akpm@linux-foundation.org, dan.j.williams@intel.com, dave.hansen@intel.com, guangrong.xiao@linux.intel.com, gleb@kernel.org, mtosatti@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, stefanha@redhat.com, yuhuang@redhat.com, linux-mm@kvack.org, ross.zwisler@linux.intel.com On Mon, 2016-09-26 at 10:46 +0200, Michal Hocko wrote: > On Fri 23-09-16 17:53:51, Oleg Nesterov wrote: > > On 09/23, Michal Hocko wrote: > > > > > > On Fri 23-09-16 15:56:36, Oleg Nesterov wrote: > > > > > > > > I think we can simplify this patch. And imo make it better. How about > > > > > > it is certainly less subtle because it doesn't report "sub-vmas". > > > > > > > if (last_addr) { > > > > vma = find_vma(mm, last_addr - 1); > > > > if (vma && vma->vm_start <= last_addr) > > > > vma = m_next_vma(priv, vma); > > > > if (vma) > > > > return vma; > > > > } > > > > > > we would still miss a VMA if the last one got shrunk/split > > > > Not sure I understand what you mean... If the last one was split > > we probably should not report the new vma. > > Right, VMA split is less of a problem. I meant to say that if the > last_vma->vm_end got lower for whatever reason then we could miss a VMA > right after. We actually might want to display such a VMA because it > could be a completely new one. We just do not know whether it is a > former split with enlarged VMA or a completely new one > > [ old VMA ] Hole [ VMA ] > [ old VMA ][ New VMa ] [ VMA ] This is indeed possible. But I see this is like the last_vma enlargement case. I suggest we accept such missing, as we accept the enlargement part of last_vma is not printed. How about we set such target: 1) no duplicate print; 2) no old vma missing (unless it's unmapped); 3) monotonic printing. We accept those newly added/changed parts between 2 partial reads is not printed. How about above suggestion? If you, Dave, Oleg and others accept it, then Oleg's improvement can achieve it, I think. > > > Nevermind, in any case yes, sure, this can't "fix" other corner cases. > > Agreed, or at least I do not see an easy way for that. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org